The timing and adjustment of internal combustion engines, especially on test stands, requires an exact measurement of, for example, the ignition angle relative to the occurrence of crankshaft positions and particularly the top dead center position (TDC). It is found experimentally that the indicated angular displacement of the TDC with respect to other events is subject to a systematic variation, in particular as a function of the engine speed. In other words, the measured interval between a signal generated at the occurrence of TDC and another signal generated at the time of occurrence of ignition is not exactly equal to the time elapsing between the corresponding crankshaft angles and, furthermore, this inexactness increases with increasing engine speed in a monotonic fashion.
In known engine test stands, a provision has been made to diminish this error by installing a function generator which generates a voltage curve that is the mirror image of the error curve and is used for its compensation. Such equipment is described for example in the German Disclosure Document No. 25 52 420. However, the provision of a separate function generator and the associated processing circuitry adds expense to the construction and opportunity for malfunction.